1. Field of the Invention
This invention relates to detecting polymer-based drag reducer additives in a gasoline sample.
2. Description of the Related Art
Polymer-based drag reducer additives are made of long chained poly-alpha-olefin polymers with ultra-high molecular weight (larger than 1-million Daltons). When injected into a stream of gasoline fuels traveling through pipelines, drag reducer additives enhances the flow of the stream by reducing effect of drag of the liquid from the pipeline walls. This, in turn, creates better streamlining for the flow in the pipe and ultimately leads to significant reductions in the cost of pipeline shipping.
As drag reducer additives injected gasoline fuels travel through pipelines, the long-chained drag reducer additives become subjected to gradual breakage mainly due to the mechanical shearing action within the pumps and pipelines. Usually, the amount of drag reducer additives to be injected in the pipeline is estimated in a way that ensures total dissipation of the long-chained polymers from the transported fuel by the time the fuel reaches its ultimate destination. In practice, however, the long-chained polymers do not totally disappear by the time they reach their end destination. There will always be some amount of intact long-chain drag reducer additives polymers remaining in the gasoline fuel at the final destination in addition to other amounts of sheared and/or partially sheared polymers.
In multi-fuel pipelines, i.e. pipelines utilized in transporting different types of gasoline fuels in sequence, extra care must be taken to achieve zero levels of drag reducer additives before transporting aviation jet fuel in particular, because aviation rules forbid the use of drag reducer additives in turbine fuel. To clean the pipeline down to zero-levels of drag reducer additives after it had been used for other drag reducer additives injected fuels the pipeline is usually flushed with some amount of drag reducer additives free fuel, such as gasoline.
A method for detecting the presence and/or concentration of drag reducer additives in gasoline fuel is based on size exclusion techniques such as gel-permeation chromatography which is relatively complicated, lengthy and expensive. The detection limit of this chromatography technique is about 1-2 PPM and can be further enhanced down to 0.2 PPM if the sample is evaporated to increase the concentration percentage of drag reducer additives. Other techniques to detect and remove drag reducer additives from gasoline fuels use absorption materials such as carbon and clay. Detection of drag reducer additives is complicated when the drag reducer additives are used with gasoline fuels. Due to the use of dilute polymeric hydrocarbons as drag reducer additives, they are indistinguishable from gasoline fuel using many of standard detection methods. In addition, drag reducer additives has no UV chromophores and, as such, it does not fluoresce when irradiated by UV light leading to challenges in using photo-optical methods for detection.
What is needed is a cost-effective method for detecting the presence and the concentration of drag reducer additives in a gasoline sample with accuracy in the PPM range. To be cost effective, it would be advantageous to provide an apparatus and method that does not require time-consuming evaporation to reach PPM accuracy, by measuring the relative intensities of specific time-gated laser-induced fluorescence fluorescence spectra that fall outside the temporal convolution area. This method can be fast and capable of detecting drag reducer additives levels in gasoline sample down to sub PPM without resorting to any evaporation procedure.